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Also play a role in amino acid degradation Above example is part of the degradation path for alanine. Transamination (transfer of the amide NH 2 to  - ketoglutarate) yields pyruvate. Pyruvate can be tossed into PDH and the Krebs cycle. Copyright  2013 Pearson Canada Inc

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Amino acid oxidases The  -amino group is usually removed by transfer to  - ketoglutarate to yield glutamate and the  -keto acid. Glutamate is then deaminated by glutamate dehydrogenase. There are also amino acid oxidases, using a flavin electron acceptor. Copyright  2013 Pearson Canada Inc

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Removal of nitrogenous waste Copyright  2013 Pearson Canada Inc Insects, birds, and reptiles primarily excrete uric acid. Desert mammals like kangaroo rats primarily excrete uric acid. Oddly, so do dalmatians. Uric acid is pretty insoluble. In humans, it is the end product of purine catabolism. Overproduction or underexcretion can lead to the formation of uric acid crystals – frequently starting in the gravitationally lowest joints – i.e. the big toe. That condition is gout, which is often extremely painful.

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Removal of nitrogenous waste – the urea cycle The universal product of degrading amino acids is ammonia. Ammonia is toxic at not very high concentrations. You have to get rid of it. If you are an aquatic organism, you can just diffuse in into the environment. We convert ammonia to urea. The basic idea: Add the nitrogens to ornithine to (eventually) make arginine. Cleave the guanidino group off arginine to leave you with ornithine and urea. Urinate out the urea. Throw the ornithine back into the cycle.

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Copyright  2013 Pearson Canada Inc

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Ammonia transport to the liver Urea formation takes place in the liver Waste nitrogen is transported through the blood as Gln or Ala. Reconverted to ammonia in the liver